1. Field of the Invention
The present invention relates generally to controlling and inhibiting the growth of microorganisms in various types of aqueous systems. More specifically, it concerns methods and compositions for inhibiting the growth of microorganisms in industrial process waters and, in particular, in pulp and paper water processing systems.
2. Description of Related Art
A major problem in industrial manufacturing is control in the growth of microorganisms in aqueous systems, especially industrial process waters. Industrial process water includes pulp and paper process water, cooling tower water, waste water, food processing water, mineral slurries, air wash water, etc.
In pulp and paper water processing systems, the warm temperatures and the high carbohydrate content result in the constant growth of microorganisms. The presence of these microorganisms presents various difficulties for paper processors. The slime caused by the presence of microorganisms results in the formation of deposits. Slime can be defined as an "accretion or accumulation caused by certain microorganisms in the presence of pulp fiber, filler, dirt and other materials, mixed in varied proportions, having variable physical characteristics and accumulating at continuously changing rates."Safade, Tackling the Slime Problem in a Paper Mill, PTI, p. 280 (September 1988). The deposits which form cause fouling, plugging, clogging, system corrosion, and breakdowns of the paper machines which result in lost production time due to work stoppages. The breaking off of loose deposits causes defective, unsalable end products which result in an economic loss for the manufacturer.
In cooling tower water, growth of microorganisms can result in loss of heat transfer efficiency, clogged tubes, and corrosion.
In mineral slurries, microorganisms can lead to discoloration and can cause odor problems. Microbiological contamination can render mineral slurries unsalable, leading to economic loss for the manufacturer.
Industrial manufacturers have conventionally dealt with these problems by applying biocides to the process waters. Biocides are typically divided into two types: oxidizing biocides such as chlorine, bromine, chlorine dioxide, ozone, and peracetic acid; and non-oxidizing biocides such as isothiazolin, methylene bisthiocyanate, glutaraldehyde, quaternary ammonium compounds, DBNPA, and bromonitrostyrene. Both types of biocides operate on microorganisms by attacking the cell wall, the cytoplasmic membrane or the cellular constituents. Although individual biocides are sometimes used by themselves, there are numerous literature references disclosing the benefits of using synergistic combinations of biocides. The benefits of synergistic combinations include reduced use rates of biocides and broader spectrum of activity, i.e., such combinations are effective against a larger number of microorganisms than each of the individual biocides alone.
Numerous references disclose the use of bromonitrostyrene with other industrial biocides for control of microbial growth. For example, U.S. Pat. No. 5,063,212 (Donofrio et al.) discloses the use of bromonitrostyrene and a biocide, such as n-tributyltetradecylphosphonium chloride. U.S. Pat. No. 4,916,164 (Whitekettle et al.) discloses the use of bromonitrostyrene and a biocide, such as 2-(decylthio)ethanamine hydrochloride. U.S. Pat. No. 4,859,708 (Donofrio et al.) discloses the use of bromonitrostyrene and a biocide, such as 2-bromo-2-nitropropane-1,3-diol. U.S. Pat. No. 3,898,343 (Swered et al.) discloses the use of bromonitrostyrene and a biocide, such as methylene bisthiocyanate.
Numerous references disclose the use of peracetic acid with other industrial biocides for control of microbial growth. For example, U.S. Pat. No. 5,368,749 (LaZonby) discloses the use of sufficient amounts of an oxidant, such as peracetic acid, and glutaraldehyde. U.S. Pat. No. 4,966,775 (Donofrio et al.) discloses the use of 2-bromo-2-nitropropane-1,3 diol and an oxidizing biocide, such as peracetic acid. U.S. Pat. No. 5,494,588 (LaZonby) discloses the use of an oxidant, peracetic acid, and a biocide, such as isothiazolin, methylene bisthiocyanate, glutaraldehyde, DBNPA, carbamate, quaternary ammonium compounds, 4,5-dichloro 1,2 dithio-3-one, and 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one or mixtures of such biocides. U.S. Pat. No. 5,658,467 (LaZonby et al.) discloses the use of an oxidant, peracetic acid, and a biocide, such as isothiazolin, methylene bisthiocyanate, glutaraldehyde, DBNPA, carbamate, quaternary ammonium compounds, 4,5-dichloro 1,2 dithio-3-one, 4,5-dichloro-2-N-octyl-4-isothiazolin-3-one, decylthioethylamine, orthophthaldehyde, 2-bromo-2-nitropropane-1,3-diol, 4,5-dichloro- 1,2-dithiol-3-one, dodecylguanidine hydrochloride, 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, dibromo dicyanobutane and bis(trichloromethyl)sulfone or mixtures of such biocides. However, none of these references disclose the combination of bromonitrostyrene and peracetic acid.